1. Preliminary
results
Dung
Doan
Crawford
School
of
Public
Policy
27
November
2012
Income and diet quality in China
2004-2009
2. Research context
Structural shift in dietary consumptions in developing
countries
Characterized not by calories deficiency, but by unbalanced diet
Significant impacts on dietary welfare, health, and labor quality
Warnings of deteriorating diet quality as income rises in China
Shift away from Chinese tradition diet
Higher consumption of animal foods and edible oils
Lower grain and vegetable consumption
Calories intake decreases
Increasing income hardly reduces vitamin A & D deficiencies
2
3. Literature review
Strong focus on diet adequacy
Levels of food and nutrient consumption as dependent variables
E.g. Berhman & Deolalikar (1987), Ravallion (1990), Skoufias (2002,
2009), Mangyo (2008)
Studies on consumption quantity are insufficient to inform about
how diet quality changes as income grows
Estimated income elasticity varies widely across studies
Consumption quantity reveals limited info about changes in diet structure
and quality
Other aspects of diet quality are under-studied, despite being
well-grounded in nutrition literature
3
4. Research questions
Does diet quality necessarily deteriorate as income rises in
China?
Are there income effects and what form do they take?
Do income effects change over time?
Are there education effects?
Contribution:
Directly examine income effects on an essential aspect of diet quality
that no economists has paid attention to: diet variety
Most recent time period
4
5. Data
5
China Health and
Nutrition Survey 2004,
2006, 2009
Multi-stage, randomized
cluster sampling design
9 provinces, approx. 3,800
households/year
Pool sample: 20,307 adults
(18-60 years old) from
4,506 households
6. Methodology
Dependent variable:
Diet variety, measured by number of major food groups consumed
Repeated cross-sectional regression models
OLS :
Poisson quasi-maximum likelihood:
where
6
7. Income effects
7
OLS
Poisson
Model
Variable
2004
2006
2009
2004
2006
2009
1
Income
0.073***
0.016
0.0092
0.064***
0.016**
0.0094*
2
Income
0.114***
0.088***
0.035***
0.114***
0.087***
0.036***
Income
squared
-‐0.0082*
-‐0.0046***
-‐0.0014***
-‐0.0094***
-‐0.0051***
-‐0.0016***
3
QuinJle
2
0.0074
0.056**
-‐0.038
0.014
0.076**
-‐0.038
QuinJle
3
-‐0.034
0.015
-‐0.043
-‐0.024
0.039
-‐0.041
QuinJle
4
0.108***
0.117***
-‐0.022
0.119***
0.137***
-‐0.018
QuinJle
5
0.138***
0.149***
0.101***
0.143***
0.159***
0.096***
*
p
<
0.10,
**
p
<
0.05,
***
p
<
0.01
Upward concave relationship between income and diet variety
Income effects vary across income groups
Income effects weaken over time
8. Income effects (cont’)
8
Marginal income effect is positive, stronger among low
income groups
Income effects weaken over time
0.00
0.02
0.04
0.06
0.08
0.10
0.12
Quintile 1 Quintile 2 Quintile 3 Quintile 4 Quintile 5
Marginal effects at mean income
2004
2006
2009
9. Education effects
Higher education attainment, higher diet diversity
Difference in impacts of vocational training and university education are
not significant at 10% level
9
OLS
Poisson
Educa=on
level
2004
2006
2009
2004
2006
2009
Primary
0.128***
0.032
0.042
0.133
0.036
0.049
Secondary
0.154***
0.106***
0.088***
0.159***
0.107***
0.095***
High
school
0.217***
0.161***
0.150***
0.217***
0.164***
0.158***
VocaJonal
training
0.322***
0.340***
0.296***
0.306***
0.321***
0.287***
University
&
above
0.338***
0.279***
0.376***
0.301***
0.243***
0.341***
*
p
<
0.10,
**
p
<
0.05,
***
p
<
0.01
Base
educaJon
category
is
“No
educaJon”
10. Preliminary conclusion
Household income has positive impact on diet variety.
Income effects are stronger among low income groups, but
diminish over time.
Education matters.
10
11. Issues and Steps forward
Refine model specification and functional form
Address issue of endogeneity between household income and
diet variety
Explore a diet quality index as a more comprehensive
measure of diet quality
11
13. Rationale for diet variety
Diet variety as dependent variable
Unambiguous and well-grounded in nutrition literature
Widely recommended by government’s dietary guidelines
Incorporated in well-known diet quality indexes
Construction of variety measure
Diet variety is most commonly measured by no. of food groups
consumed (Ruel 2005)
Food group classification is based Chinese Food Composition Table
(Yang et al. 2004, 2009), Chinese dietary guidelines 2007, and Diet
quality index – International (Kim et al. 2003)
13
14. Income effects
Upward concave relationship between income and diet variety
Marginal income effect is smaller among high income groups
Income effects weaken over time – flatter curves
Note: The curves represent the predicted quadratic relationship between income and diet variety, while holding all other
regressors constant. Thus, values on the vertical axis do not represent nominal value of diet variety.
14
-
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0 3 6 9 12 15 18
Predicteddietvariety
Household income per capita (10,000 Yuan)
Predicted diet variety based on Model 2 and mean income of percentiles
2004
2006
2009
15. Income marginal effects
Marginal income effect is smaller among high income groups
Need to refer to nutrition literature to assess the benefit of
having 1 additional food group in diet
15
OLS
Poisson
Income
Marginal
effect
2004
2006
2009
2004
2006
2009
Sample
mean
0.099
0.078
0.031
0.097
0.076
0.031
Mean
of
quinJle
1
0.112
0.086
0.034
0.111
0.086
0.035
Mean
of
quinJle
2
0.108
0.084
0.033
0.107
0.083
0.034
Mean
of
quinJle
3
0.104
0.081
0.032
0.102
0.080
0.032
Mean
of
quinJle
4
0.097
0.077
0.030
0.094
0.075
0.030
Mean
of
quinJle
5
0.076
0.061
0.024
0.070
0.058
0.023
16. Compare Model 2 and Model 3
16
0.00
0.05
0.10
0.15
0.20
0.25
Quintile 2 Quintile 3 Quintile 4 Quintile 5
Income effects, as compared to Quintile 1
2004 - model 2 2006 - model 2 2009 - model 2
2004 - model 3 2006 - model 3 2009 - model 3
17. Community-fixed effects
OLS
Poisson
Province
2004
2006
2009
2004
2006
2009
Heilongjiang
-‐0.011
-‐0.049
-‐0.088**
-‐0.0038
-‐0.0392
-‐0.076*
Jiangsu
-‐0.3889**
-‐0.706***
-‐0.797***
-‐0.347***
-‐0.617***
-‐0.718***
Shandong
-‐0.289***
-‐0.690***
-‐0.487***
-‐0.247***
-‐0.641***
-‐0.419***
Henan
-‐0.359***
-‐0.642***
-‐0.625***
-‐0.316***
-‐0.568***
-‐0.564***
Hubei
-‐0.683***
-‐0.917***
-‐0.894***
-‐0.670***
-‐0.879***
-‐0.849***
Hunan
-‐0.453***
-‐0.800***
-‐0.881***
-‐0.434***
-‐0.722***
-‐0.829***
Guangxi
-‐0.838***
-‐1.216***
-‐1.175***
-‐0.991***
-‐1.369***
-‐1.088***
Guizhou
-‐0.435***
-‐0.6623***
-‐0.600***
-‐0.395***
-‐0.587***
-‐0.492***
• p
<
0.10,
**
p
<
0.05,
***
p
<
0.01
• Base
province
is
Liaoning
17
Provincial factors play a significant role in determining diet
variety
Considerable differences across some provinces
19. Descriptive Statistics
19
No.
of
food
groups
consumed
2004
2006
2009
Mean
1.72
1.77
1.89
Median
2
2
2
Standard
deviaJon
0.77
0.80
0.83
Percentage
0
0.24%
0.31%
0.10%
1
43.38%
41.76%
36.25%
2
43.30%
41.25%
42.18%
3
10.43%
13.85%
17.94%
4
2.36%
2.56%
3.15%
5
0.29%
0.28%
0.39%
HH
income
pc
(Yuan),
adjusted
to
adult
equivalence
scale
2004
2006
2009
Sample
mean
9,111
10,828
14,951
Mean
of
quinJle
1
1,352
1,505
1,622
Mean
of
quinJle
2
3,899
4,123
6,481
Mean
of
quinJle
3
6,439
7,219
10,442
Mean
of
quinJle
4
10,455
11,649
16,682
Mean
of
quinJle
5
23,256
28,671
38,782
20. Dietary guidelines for Chinese residents
20
1.
Eat
a
variety
of
foods,
mainly
cereals
including
appropriate
amount
of
coarse
grains
2.
Consume
plenty
of
vegetables,
fruits
and
tubers
3.
Consume
milk,
soybean
or
dairy-‐
or
soybean-‐products
everyday
4.
Consume
appropriate
amounts
of
fish,
poultry,
eggs
and
lean
meat
5.
Use
less
cooking
oil;
choose
a
light
diet
which
is
also
low
in
salt
6.
Do
not
over
eat,
exercise
every
day,
and
maintain
a
healthy
body
weight
7.
RaJonally
distribute
the
daily
food
intake
among
the
three
meals,
correctly
choose
snacks
8.
Drink
sufficient
amount
of
water
every
day,
raJonally
select
beverages
9.
If
you
drink
alcoholic
beverages,
do
so
in
limited
amounts
10.
Choose
fresh
and
sanitary
foods
Source: Ke (2011)
21. Food classification
21
Food
groups
Foods
sub-‐groups
Grain
Wheat,
rice,
corn,
barley,
millet,
tubers
Vegetable
Root,
stem,
leafy,
and
flowering
vegetables
Fruit
Fruits
Meat
Pig,
cakle,
mukon,
poultry
,
fish,
egg,
beans,
and
products
Dairy
Milk
and
dairy
products
Others
Fungi,
nuts
&
seeds,
infant
food,
ethnic
foods
&
cakes,
fast
foods,
beverages,
alcoholic
beverages,
sugars
&
preserves
&
honey,
fats
&
vegetable
oils,
condiments
Source: Chinese Food Composition Tables (Yang et al. 2004, 2009)
